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Copyright Brian J. Kirby. With questions, contact Prof. Kirby here. This material may not be distributed without the author's consent. When linking to these pages, please use the URL http://www.kirbyresearch.com/textbook.

This web posting is a draft, abridged version of the Cambridge University Press text. Follow the links to buy at Cambridge or Amazon or Powell's or Barnes and Noble. Contact Prof. Kirby here. Click here for the most recent version of the errata for the print version.

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Jump To: [Kinematics] [Couette/Poiseuille Flow] [Fluid Circuits] [Mixing] [Electrodynamics] [Electroosmosis] [Potential Flow] [Stokes Flow] [Debye Layer] [Zeta Potential] [Species Transport] [Separations] [Particle Electrophoresis] [DNA] [Nanofluidics] [Induced-Charge Effects] [DEP] [Solution Chemistry]

B.2 Aqueous solutions and key parameters [water properties top]

We use the term aqueous solutions to describe solutions of water with dissolved solutes. We use the term electrolyte solutions to define solutions where some or all of the solutes are ionized, and we use the term electrolyte torefer to the ionized solutes. Each species of electrolyte has a number of properties, including molar concentration, normality, and valence. Molarconcentration c is defined as
microfluidics textbook nanofluidics textbook Brian Kirby Cornell
(B.1)

and is expressed in units of molar or M. For example, 1×10-3 moles in 1×10-1liters is 1×10-2 M or 10 mM. One mole is equal to NA or 6.02×1023 molecules. Since a liter is not an SI unit (1 L=1×10-3 m3), M is not an SI unit. Normalityof a species is a measure of the number of H+ or OH- available to be gained or lost per liter of solution. Thus 1 M of H2SO4 is 2 N, because two H+ ions dissociate per H2SO4 molecule. The valenceor charge number z of an ion is the charge of the ion, normalized by the elementary charge. For example, the valence of Na+ is 1, and the valence of SO4-2 is -2. A solution in total has an ionicstrength, written as Ic and given by:
microfluidics textbook nanofluidics textbook Brian Kirby Cornell
(B.2)

where i refers to an individual chemical species. For example, for 2M KCl, Ic = 2M, and for 2M MgSO4, Ic = 8M. Certain solutions are described as being made up of symmetricelectrolytes. A symmetric electrolyte is an electrolyte system in which the magnitude of the charge of the anion and cation are the same. Examples include NaCl and MgSO4.

These solutes have a number of transport properties, such as diffusivity, electrophoretic mobility, and molar conductivity, which are described in Chapter 11. They also have dielectric properties such as the dielectric increment, described in Section B.4.

[Return to Table of Contents]



Jump To: [Kinematics] [Couette/Poiseuille Flow] [Fluid Circuits] [Mixing] [Electrodynamics] [Electroosmosis] [Potential Flow] [Stokes Flow] [Debye Layer] [Zeta Potential] [Species Transport] [Separations] [Particle Electrophoresis] [DNA] [Nanofluidics] [Induced-Charge Effects] [DEP] [Solution Chemistry]

Copyright Brian J. Kirby. Please contact Prof. Kirby here with questions or corrections. This material may not be distributed without the author's consent. When linking to these pages, please use the URL http://www.kirbyresearch.com/textbook.

This web posting is a draft, abridged version of the Cambridge University Press text. Follow the links to buy at Cambridge or Amazon or Powell's or Barnes and Noble. Contact Prof. Kirby here. Click here for the most recent version of the errata for the print version.


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